Diastema closure can be a challenging restorative process. The key to success is proper treatment planning and creating a vision of the desired outcome. This “outcome-based” design provides the guidance needed to create esthetic, cleansable and long-lasting restorations.

When a patient presents with the desire to close a diastema, it is important to first apply the treatment planning concepts of Facially Generated Treatment Planning (FGTP) to guide the proposed restorative process. Using FGTP templates, the tooth contours may be evaluated to determine the correct tooth proportion with the closure of the interproximal space. From these templates, a diagnostic wax-up may be created to provide guidance for tooth preparation finish lines and margins. The placement of these lines is critical to longevity and maintainability of the restorations.

There is a general “rule of thumb” for finish line positions when closing open contact situations. Generally, for teeth ideally positioned within the dental arches, the contact point between the anterior teeth is positioned directly under the peak of the gingival papilla. This positioning allows for adequate facial, incisal and gingival embrasure form of the teeth. To close open contact situations, it is important for the restorative dentist to correctly position the finishing lines of the restoration.

The “rule of thumb” suggests that if there is one millimeter between the roots of the teeth, the lingual finish line of the veneer should be one millimeter palatal to the papilla (or contact point). If two millimeters exist between the roots, then the finish line should be two millimeters (minimum) palatal to the contact. If there is three millimeters between the roots, then the new contact should be positioned three millimeters to the lingual. Beyond that, orthodontics or tooth movement should be considered as a tool for closing contacts.

If the lingual finishing line is positioned too facial, there is risk that the final veneer ceramic will have a “wing” of unsupported ceramic and the “wing” will create an interproximal “ledge” that will be impossible to floss and clean adequately. This “rule of thumb” is a guide for achieving predictable results. By applying these concepts to a case, it may be easier to visualize the end goal.

pre treatment diastema
Figure 1: Pre-treatment #8 and 9 Diastema

Dick C. presented to my practice with a desire to close his maxillary anterior diastema. No medical complications existed to limit his treatment. He was not interested in pursuing orthodontics.

FGTP planning template
Figure 2: FGTP Planning Templates

Facially Generated Treatment Planning templates were utilized to guide the patient conversation and treatment planning. It was decided to utilize two anterior veneers to achieve the desired result.

tooth preparation margin design
Figure 3: Tooth preparation margin design - 2mm lingual to contact point.

Using the “rule of thumb” as a guide, the papilla between the adjacent central incisors was identified. The incisal edges of the proposed veneers are determined, and a line is extended from the distal aspect of each central incisor. This line aids in visualizing the contact points between the tooth surfaces. In the image provided, an approximation of the veneer tooth preparations is outlined. The margins are identified according to the “rule of thumb.”

The dimension of the midline diastema is approximately 1mm. This infers that the midline root proximity is 2mm. The “rule of thumb” guideline requires that the veneer margin be placed 2mm palatal to the midline papilla. The distal contacts of the proposed veneers will remain in their existing positions. Therefore, the distal margins will be placed 1 mm palatal to the contact point.

final veneer preparations
Figure 4: Final veneer prepearations - finish line 2mm lingual to contact.

An image of the final veneer preparations shows the actual placement of the interproximal finishing lines. The midline finish lines are 2mm lingual to the contact point. The distal margins were placed one millimeter palatal to the contact. These margin placements allow for them to be cleansed and to allow for adequate ceramic thickness.

final veneers
Figure 5: Final Veneers #8 and 9

The ceramic veneers on the models provide clear observation to the placement differences between the mesial and distal finished margins. Placing the margins with the proper palatal extension allows for a smooth transition line from natural tooth structure to the ceramic veneer. This contour allows for adequate and successful home care.

final pressed emax veneers
Figure 6: Final Pressed Emax Veneers #8 and 9

These finished restorations have properly closed the patient's midline diastema. Dick C. is very pleased with the results. The margin placement has allowed for healthy tissue and ideal papilla form. Applying the “rule of thumb” concepts to margin placement helps to create restorative results that are predictable and long lasting. The process begins with “outcome-based” design and planning. By knowing where we want to go from the beginning, it is possible to execute the process with precision and predictability.

Jeffrey Bonk, D.D.S., is a member of Spear Resident Faculty.